<h2>DESCRIPTION</h2>

<em>r.li.patchdensity</em> calculates the "patch density index", 
the number of patches per square kilometer, as:
<div class="code"><pre>
PD = Npatch / A
</pre></div>

with:
<ul>
  <li><b>A</b>:sampling area size</li>
  <li><b>Npatch</b>: number of patches</li>
</ul>

<p>
This index is calculated using a 4 neighbour algorithm, diagonal cells 
are ignored when tracing a patch.

<h2>NOTES</h2>

Do not use absolute path names for the <b>config</b> and <b>output</b>
file/map parameters.

If the "moving window" method was selected in <b>g.gui.rlisetup</b>, then the
output will be a raster map, otherwise an ASCII file will be generated in
the folder <tt>C:\Users\userxy\AppData\Roaming\GRASS8\r.li\output\</tt>
(MS-Windows) or <tt>$HOME/.grass8/r.li/output/</tt> (GNU/Linux).
<p>
A sample area of only NULL values is considered to have zero patches, 
that is, the result is always &ge; 0.

<h2>EXAMPLES</h2>
To calculate patch density index on map <em>my_map</em>, using
<em>my_conf</em> configuration file (previously defined with
<em>g.gui.rlisetup</em>) and saving results in <em>my_out</em>, run:
<div class="code"><pre>
r.li.patchdensity input=my_map conf=my_conf output=my_out
</pre></div>

<p>
Example for Spearfish forest areas:
<div class="code"><pre>
g.region raster=landcover.30m -p
# extract forested areas:
r.category landcover.30m
r.mapcalc "forests = if(landcover.30m >= 41 && landcover.30m <= 43, 1, null())"

# patch density (7x7 moving window defined in g.gui.rlisetup):
r.li.patchdensity forests conf=movwindow7 out=forests_p_dens7
r.univar forests_p_dens7
d.rast.leg forests_p_dens7

r.to.vect forests out=forests feature=area
d.vect forests type=boundary
</pre></div>
<p>

Forest map (North Carolina sample dataset) example:
<div class="code"><pre>
g.region raster=landclass96 -p
r.mapcalc "forests = if(landclass96 == 5, 1, null() )"
r.li.patchdensity input=forests conf=movwindow7 out=forests_patchdensity_mov7

# verify
r.univar forests_patchdensity_mov7
r.to.vect input=forests output=forests type=area
d.mon wx0
d.rast forests_patchdensity_mov7
d.vect forests type=boundary
</pre></div>

<h2>SEE ALSO</h2>
<em>
<a href="r.li.html">r.li</a> - package overview<br>
<a href="g.gui.rlisetup.html">g.gui.rlisetup</a>
</em>

<h2>REFERENCES</h2>
McGarigal, K., and B. J. Marks. 1995. FRAGSTATS: spatial pattern
analysis program for quantifying landscape structure. USDA For. Serv.
Gen. Tech. Rep. PNW-351. (<a href="http://treesearch.fs.fed.us/pubs/3064">PDF</a>)

<h2>AUTHORS</h2>
Michael Shapiro - CERL (patch identification)<br>
Markus Metz (statistics)

<!--
<p>
<i>Last changed: $Date$</i>
-->
